Implements linter for pkg/hold missing warnings

pkg/hold/admin/admin.go

···
 
 // Session management
 
-func (ui *AdminUI) createSession(did, handle string) string {
+func (ui *AdminUI) createSession(did, handle string) (string, error) {
 	b := make([]byte, 32)
-	rand.Read(b)
+	if _, err := rand.Read(b); err != nil {
+		return "", fmt.Errorf("failed to create session token: %w", err)
+	}
 	token := base64.URLEncoding.EncodeToString(b)
 
 	ui.sessionsMu.Lock()
 	ui.sessions[token] = &AdminSession{DID: did, Handle: handle}
 	ui.sessionsMu.Unlock()
 
-	return token
+	return token, nil
 }
 
 func (ui *AdminUI) getSession(token string) *AdminSession {
···
 
 	w.Header().Set("Content-Type", "application/json")
 	w.Header().Set("Cache-Control", "public, max-age=3600")
-	json.NewEncoder(w).Encode(metadata)
+	if err := json.NewEncoder(w).Encode(metadata); err != nil {
+		slog.Error("failed to encode json to http response", "error", err, "path", r.URL.Path)
+		w.WriteHeader(http.StatusInternalServerError)
+	}
 }
 
 // Close cleans up resources (no-op now, but keeps interface consistent)

pkg/hold/admin/handlers.go

···
 
 	// Otherwise return JSON
 	w.Header().Set("Content-Type", "application/json")
-	json.NewEncoder(w).Encode(stats)
+	if err := json.NewEncoder(w).Encode(stats); err != nil {
+		slog.Error("failed to encode json to http response", "error", err, "path", r.URL.Path)
+		w.WriteHeader(http.StatusInternalServerError)
+	}
 }
 
 // UserUsage represents storage usage for a user
···
 
 	// Otherwise return JSON
 	w.Header().Set("Content-Type", "application/json")
-	json.NewEncoder(w).Encode(users)
+	if err := json.NewEncoder(w).Encode(users); err != nil {
+		slog.Error("failed to encode json to http response", "error", err, "path", r.URL.Path)
+		w.WriteHeader(http.StatusInternalServerError)
+	}
 }

pkg/hold/admin/handlers_auth.go

···
 	}
 
 	// Create session and set cookie
-	token := ui.createSession(did, handle)
+	token, err := ui.createSession(did, handle)
+	if err != nil {
+		slog.Error("failed to create session token", "error", err, "path", r.URL.Path)
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
 	ui.setSessionCookie(w, r, token)
 
 	slog.Info("Admin login successful", "did", did, "handle", handle)

pkg/hold/admin/handlers_crew.go

···
 
 		// Re-apply tier to new record
 		if tier != "" {
-			ui.pds.UpdateCrewMemberTier(ctx, current.Member, tier)
+			if err := ui.pds.UpdateCrewMemberTier(ctx, current.Member, tier); err != nil {
+				slog.Error("failed to update crew member tier", "error", err, "path", r.URL.Path)
+				w.WriteHeader(http.StatusInternalServerError)
+				return
+			}
 		}
 	}